Dataset Information

Adaptation of Cyanobacteria to the Endolithic Light Spectrum in Hyper-Arid Deserts.

ABSTRACT: In hyper-arid deserts, endolithic microbial communities survive in the pore spaces and cracks of rocks, an environment that enhances water retention and filters UV radiation. The rock colonization zone is enriched in far-red light (FRL) and depleted in visible light. This poses a challenge to cyanobacteria, which are the primary producers of endolithic communities. Many species of cyanobacteria are capable of Far-Red-Light Photoacclimation (FaRLiP), a process in which FRL induces the synthesis of specialized chlorophylls and remodeling of the photosynthetic apparatus, providing the ability to grow in FRL. While FaRLiP has been reported in cyanobacteria from various low-light environments, our understanding of light adaptations for endolithic cyanobacteria remains limited. Here, we demonstrated that endolithic Chroococcidiopsis isolates from deserts around the world synthesize chlorophyll f, an FRL-specialized chlorophyll when FRL is the sole light source. The metagenome-assembled genomes of these isolates encoded chlorophyll f synthase and all the genes required to implement the FaRLiP response. We also present evidence of FRL-induced changes to the major light-harvesting complexes of a Chroococcidiopsis isolate. These findings indicate that endolithic cyanobacteria from hyper-arid deserts use FRL photoacclimation as an adaptation to the unique light transmission spectrum of their rocky habitat.

SUBMITTER: Murray B

PROVIDER: S-EPMC9228357 | biostudies-literature | 2022 Jun

REPOSITORIES: biostudies-literature

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Adaptation of Cyanobacteria to the Endolithic Light Spectrum in Hyper-Arid Deserts.

Murray Bayleigh B Ertekin Emine E Dailey Micah M Soulier Nathan T NT Shen Gaozhong G Bryant Donald A DA Perez-Fernandez Cesar C DiRuggiero Jocelyne J

Microorganisms 20220611 6

In hyper-arid deserts, endolithic microbial communities survive in the pore spaces and cracks of rocks, an environment that enhances water retention and filters UV radiation. The rock colonization zone is enriched in far-red light (FRL) and depleted in visible light. This poses a challenge to cyanobacteria, which are the primary producers of endolithic communities. Many species of cyanobacteria are capable of Far-Red-Light Photoacclimation (FaRLiP), a process in which FRL induces the synthesis o ...[more]

PMID: 35744716

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Project description:Under extreme water deficit, endolithic (inside rock) microbial ecosystems are considered environmental refuges for life in cold and hot deserts, yet their diversity and functional adaptations remain vastly unexplored. The metagenomic analyses of the communities from two rock substrates, calcite and ignimbrite, revealed that they were dominated by Cyanobacteria, Actinobacteria, and Chloroflexi. The relative distribution of major phyla was significantly different between the two substrates and biodiversity estimates, from 16S rRNA gene sequences and from the metagenomic data, all pointed to a higher taxonomic diversity in the calcite community. While both endolithic communities showed adaptations to extreme aridity and to the rock habitat, their functional capabilities revealed significant differences. ABC transporters and pathways for osmoregulation were more diverse in the calcite chasmoendolithic community. In contrast, the ignimbrite cryptoendolithic community was enriched in pathways for secondary metabolites, such as non-ribosomal peptides (NRP) and polyketides (PK). Assemblies of the metagenome data produced population genomes for the major phyla found in both communities and revealed a greater diversity of Cyanobacteria population genomes for the calcite substrate. Draft genomes of the dominant Cyanobacteria in each community were constructed with more than 93% estimated completeness. The two annotated proteomes shared 64% amino acid identity and a significantly higher number of genes involved in iron update, and NRPS gene clusters, were found in the draft genomes from the ignimbrite. Both the community-wide and genome-specific differences may be related to higher water availability and the colonization of large fissures and cracks in the calcite in contrast to a harsh competition for colonization space and nutrient resources in the narrow pores of the ignimbrite. Together, these results indicated that the habitable architecture of both lithic substrates- chasmoendolithic versus cryptoendolithic - might be an essential element in determining the colonization and the diversity of the microbial communities in endolithic substrates at the dry limit for life.

Project description:It is often difficult to decide which cyanobacteria found in endolithic habitats of calcite spring-tufa deposits are present as ephemeral components of the biota or are persistent, structural elements. To answer this question, we repeatedly studied two microhabitats of contrasting calcareous tufa springs in the European Alps. Pigment extracts, fluorescence probe measurements of in situ samples and traditional microscopy confirmed the dominance of cyanobacteria over eukaryotic algae and their viability in both microhabitats. Spring Site 1 (Laas, Northern Italy) is characterized by a highly variable, moist to dry and sun-exposed waterfall tufa consisting of fibrous calcite. A segment of these deposits in the lateral flank of a grotto contained dark endolithic layers in dim light, 1-2 mm below the surface, where aggregated cyanobacterial cells were dominant but not directly attached to calcites, a potential sign of gentle endolithic dissolution rather than calcite precipitation induced by cyanobacteria. Site 2 (Mühlau, Austria), in contrast, is a moss-tufa microhabitat associated with a seepage spring situated in a shady gorge, where the targeted stromatolites consisted of bark-like sheets of friable, orange to light-brown when wet (drying violet) 'styrofoam'- like aggregates of minute crystallites on the day-light exposed surfaces. These calcites were observed to nucleate directly on external sheaths of viable cyanobacteria trichomes. A polyphasic approach including LM, SEM, TEM exhibited a number of identical but also some divergent cyanobacteria of which two key taxa were specific for each of the two microhabitats (Nostoc and Pseudoscytonema at Sites 1 and 2 respectively). Both cyanobacterial communities characterised, by the cloning of 16S rDNA showed a dominance of mostly unknown and partly divergent filamentous cyanobacteria assigned to the order of Synechococcales. Our microhabitat study of alpine crenal calcites highlights the rather divergent biotic responses of cyanobacteria within spring tufa deposits.

Dataset Information

Adaptation of Cyanobacteria to the Endolithic Light Spectrum in Hyper-Arid Deserts.

Publications

Adaptation of Cyanobacteria to the Endolithic Light Spectrum in Hyper-Arid Deserts.

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